covalent bond

Good plasticity, stable chemical properties, not easy to hydrolyze, but average mechanical strength, low carbon-hydrogen bond energy, and poor heat resistance

The heat resistance and strength are higher than those of carbon chain polymers, but the chemical properties are unstable due to the introduction of functional groups.

No carbon atoms in the main chain

Good plasticity and elasticity

Excellent thermal stability

Less intense

Soft and elastic, it can be dissolved in an appropriate solvent, can be spun into silk, can be formed into a film, and can be thermoformed into products of various shapes. It is usually called a thermoplastic polymer.

Loosely packed, low density, low crystallinity, strong air permeability

Network macromolecules, good heat resistance, high strength, strong solvent resistance, stable shape

The RS configuration is formed in the C atom space of four different substituents.

Total isomorphism

syndiomorphism

random configuration

Isotactic and syndiotactic polymers are stereoregular polymers

Caused by different configurations of substituents on double bonds or ring structures in polymer molecules

The polymer has good stereoregularity and orderly arrangement of molecules, which is conducive to crystallization. High crystallinity leads to high boiling point, high melting point, high strength, and high solvent resistance.

The more structural units each chain segment contains, the smaller the flexibility.

C-O C-N Si-O can increase flexibility

Benzene ring or conjugated double bond,

isolated double bond

substituent

Hydrogen bonding greatly increases the rigidity of the molecular chain and reduces the flexibility. The impact is more significant than polarity.

Cross-linking reduces flexibility

Regardless of bond angle restrictions and potential barrier obstacles, each polymer chain is composed of many chemical bonds freely linked, and each bond has an equal chance of being oriented in any direction.

Each bond is free to rotate in the direction allowed by the bond angle, but the effect of steric hindrance on rotation is not considered.

Consistent with the geometric algorithm results

The actual polymer chain is not a freely connected chain or a freely rotating chain. A bond originally composed of n bonds with a bond length of l and a fixed bond angle of θ and non-rotatable bonds is actually an equivalent free connection chain composed of Z chain segments of length b.

The energy required to overcome the intermolecular forces and move one mole of liquid or solid molecules beyond their gravitational pull.

The shortcut to polymers is not 100%

Can be expressed as weight percentage and volume percentage

density method

x-ray diffraction

differential scanning calorimetry

Infrared spectroscopy

The higher the crystallinity, the greater the strength, and the lower the elasticity, elongation, and impact toughness.

The smaller the spherulite size, the higher the strength and toughness.

Density increases with increasing crystallinity

The higher the crystallinity, the worse the transparency

The higher the crystallinity, the better the heat resistance

The higher the crystallinity, the worse the breathability and solubility.

Tmax≈0.85Tm

The simpler the structure, the higher the symmetry, the smaller the steric hindrance of the substituents, the better the stereoregularity, and the faster the crystallization rate.

Low molecular weight and fast crystallization

forming conditions

Arrangement